wtheme.theme

<?php

/**
 * @file
 * Functions to support theming in the wtheme theme.
 */

/**
 * Implements template_preprocess_HOOK() for the HTML template.
 */
function wtheme_preprocess_html(&$variables) {

  // Add node id as a class.
  $request = \Drupal::request();
  $node = ($request->attributes->get('_route') == 'entity.node.canonical' ? $request->attributes->get('node') : NULL );

  if ($node) {
    $variables['attributes']['class'][] = 'page-node-' . $node->id();
  }

  /* Add information about presence of sidebars.
  .sidebar-first.sidebar-second means class for two sidebars. */

  $has_first_sidebar = !empty($variables['page']['sidebar_first']);
  $has_second_sidebar = !empty($variables['page']['sidebar_second']);

  if ($has_first_sidebar) {
    $variables['attributes']['class'][] = 'layout-sidebar-first';
  }
  elseif ($has_second_sidebar) {
    $variables['attributes']['class'][] = 'layout-sidebar-second';
  }
  else {
    $variables['attributes']['class'][] = 'layout-no-sidebars';
  }
}